The present invention relates to a fuel adsorption filter for adsorbing fuel vapor leaking from the intake system of an internal combustion engine such as an automobile engine, and to an air cleaner having the fuel adsorption filter.
Conventionally, for example, Japanese Laid-Open Patent Publication Nos. 2003-42017 and 2003-120445 each disclose an air filter having this type of fuel adsorption filter.
In the configuration disclosed in Japanese Laid-Open Patent Publication No. 2003-42017, an air filter is incorporated in a housing having an air inlet and an air outlet. The air filter traps dust in intake air supplied to the intake system of an internal combustion engine. In the housing, a sheet-like fuel adsorption filter having a fuel adsorbent such as activated carbon is located downstream of the air filter. The fuel adsorption filter is arranged orthogonal to the passage of air. The fuel adsorption filter adsorbs fuel vapor leaking from the intake system of the internal combustion engine.
Like the configuration of Japanese Laid-Open Patent Publication No. 2003-42017, the configuration of Japanese Laid-Open Patent Publication No. 2003-120445 includes an air filter incorporated in a housing with an air inlet and an air outlet. The air filter traps dust in intake air. On the downstream side of the air filter, a block-like fuel adsorption canister having a fuel adsorbent such as activated carbon is located in an inner bottom portion of the housing. The canister is arranged to partially intersect the passage of air. The fuel adsorption canister adsorbs fuel vapor leaking from the intake system of the internal combustion engine.
The above described conventional configurations have the following drawbacks.
That is, in the conventional configuration of Japanese Laid-Open Patent Publication No. 2003-120445, the sheet-like fuel adsorption filter is arranged in the entirety of an area that intersects the air passage on the downstream side of the air filter. The fuel adsorption filter increases the flow resistance in the air cleaner, thereby lowering the operation efficiency of the internal combustion engine. Further, since the fuel adsorption filter faces the entire area of the air passage, the combustion pressure in a backflow direction of the air flow is hardly released in a case of a backfire, and directly acts on the fuel adsorption filter. This can damage the fuel adsorption filter and attaching portions of the filter.
Also, the block-like fuel adsorption canister of Japanese Laid-Open Patent Publication No. 2003-120445 is arranged in a part of the passage downstream of the air filter without facing the entire area of the downstream side of the air filter. The canister thus cannot effectively adsorb fuel vapor leaking from the intake system of the internal combustion engine, and may allow the fuel vapor to be discharged to the atmosphere. To avoid such a drawback, the size of the fuel adsorption canister may be increased, so that its adsorption area is enlarged. However, this increases the flow resistance in the air cleaner, resulting in a lowered operation efficiency of the internal combustion engine.
The present invention was made for solving the above problems in the prior art. It is an objective of the present invention to provide a fuel adsorption filter and an air cleaner that effectively adsorb leaked fuel vapor, reduce flow resistance, and prevent damages caused by backfires.